Generally with any traffic source it is good practice to separate device types as different campaigns.
Main reason is that the bids might be very different for mobile vs. desktop (depending on demand).
Imagine if mobile is cheaper than desktop, but you bid together in once campaign, what happens is that you will OVERPAY the mobile, and UNDERPAY the desktop.
Hope it makes sense.
On native I also believe there could be totally different placements for mobile/desktop version of the sides.
Divide and conquer! 
I also separate mobile/desktop/tab ... different bids are the main reason for me, then there is the fact that different device-traffic can respond better to different LPs and offer urls. When separated, it's way easier to analyze the data.
I'm testing this strategy on a different traffic source now. Will let you know what happens.
Side note I see you're also a transplant from madsociety - what prompted the move?
You'll never know if you don't try
Separate is certainly the norm, but who knows why the native gods choose one thing to work vs another, so it's definitely possible you're campaign could perform better with all three
You could always leave the successful one up and just try three separate ones too, that way if they don't work better your original is still up and going.
By the way great work on that sucker! Very cool stuff man
Are you still on the DSP or did you switch to direct?
I actually asked Ralfs the other day if he still does this and recommends and he gave a resounding yes.
However I would imagine this type of thing works best on Taboola due to smart bid.
My experience has been that certain bid thresholds exempt pretty much the majority of more expensive device types, so while I wasn't getting really any desktop traffic in my 'mobile' campaign on Taboola, I was getting some tablet.
On Revcontent I'm not so sure that approach is the best, but regardless I would be moving towards an autoboost campaign per device type as soon as you've build up a good amount of conversion data. Once that's going then it would be worth testing an all devices campaign, but I never personally tested that.